Someone else recommended the SprintBooster. Would this mod void warranty or be something the service dept. might have a problem with? Also, do you think a CAI would help this particular problem?

IMHO, the SprintBooster or equivalent shouldn't void the warranty as it is considered a bolt-on mod, but it really is up to the discretion of your Dealership's Service Dept. A CAI may help a little bit, but due to the nature of drive-by wire systems the delay will still be there to some extent.